Instructions for making The Liberator, a plastic handgun that could escape detection by conventional airport security, were today made freely available to download from the internet by anti-government activists in the US.

It was created by a group in Texas that aims to make â€œWikiWeaponsâ€ that can be reproduced with a home computer and a $1,000 (Â£644) 3D printer that uses heated plastics instead of ink.

â€œItâ€™s a demonstration that technology will allow access to things that governments would otherwise say that you shouldnâ€™t have access to,â€ Cody Wilson, the leader of Defense Distributed, told The Daily Telegraph.

â€œThings that there are legitimate demands for will be available,â€ said Mr Wilson, 25, who is described as a free-market anarchist. â€œThatâ€™s the point we want to make.â€